Techniques for forming a polymer image by photopolymerization in which an organic dye is used as a photosensitizer (photopolymerization initiator) are well known, but the sensitivity reached by these techniques is generally ISO 10.sup.-3 or less (ISO: International Organization for Standardization), which is far inferior to the sensitivity of silver halide photographic materials. Various attempts have heretofore been made in which a silver halide is used as a trigger and the high amplification degree thereof in a development process is utilized for initiation of the polymerization reaction.
For example, Japanese Patent Publication No. 6581/71 and, Japanese Patent Application (OPI) Nos. 138632/82, 142638/82, 176033/82, 107529/83, 169143/83 and 174947/83 (the term "OPI" as herein used means "published unexamined application") and U.S. Pat. Nos. 3,707,379, 3,767,400, 3,782,943, 3,697,273, 3,756,818, 3,687,667, 3,874,947, 3,756,820 and 3,746,542 describe a polymerization method in which the polymerization reaction is initiated by a radical derived from a reducing agent oxidized during development of silver halide. U.S. Pat. No. 3,241,962 describes a polymerization method in which the polymerization reaction is initiated by a radical derived from a peroxide upon redox reaction with a silver image obtained by development of a silver halide. U.S. Pat. No. 3,345,164 discloses a method in which the polymerization reaction is initiated by a radical derived from a peroxide upon redox reaction with a silver ion remaining in non-exposed areas which is dissolved out after development of a silver halide. U.S. Pat. No. 3,029,145 discloses a method in which the polymerization reaction is initiated by a radical derived from a peroxide upon redox reaction with an iron (I) salt remaining in non-exposed areas after development of a silver halide with an iron (I) salt. Further, Japanese Patent Application (OPI) No. 149939/80 teaches a method in which the polymerization reaction is directly initiated by a reducing agent remaining in non-exposed areas after development of a silver halide.
In these methods, a radical is generated directly or after successive reaction from any of raw materials (i.e., silver halide or reducing agent) or products (i.e., silver image or oxidation product of reducing agent) which participate in the development of a silver halide. According to these methods, it is assumed that a polymer image is formed with a sensitivity near to that of a silver halide. However, the above methods all involve a wet process in the development of silver halide and the polymerization in the presence of a radical. Further, the methods using a peroxide are disadvantageous in that dark polymerization takes place in the presence of a radical formed by decomposition of the peroxide, which results in serious deterioration of recording materials and the occurrence of fog. In addition, the polymerization reaction according to these methods generally requires a long time period.